Application of a model of plastic porous materials including void shape effects to the prediction of ductile failure under shear-dominated loadings

International audienceAn extension of Gurson's famous model (Gurson, 1977) of porous plastic solids, incorporating void shape effects, has recently been proposed by Madou and Leblond (Madou and Leblond, 2012a,b, 2013; Madou et al., 2013). In this extension the voids are no longer modelled as spherical but ellipsoidal with three different axes, and changes of the magnitude and orientation of these axes are accounted for. The aim of this paper is to show that the new model is able to predict softening due essentially to such changes, in the absence of significant void growth. This is done in two steps. First, a numerical implementation of the model is proposed and incorporated into the SYSTUS and ABAQUS finite element programmes (through some freely available UMAT (Leblond, 2015) in the second case). Second, the implementation in SYSTUS is used to simulate previous " numerical experiments " of Tvergaard and coworkers (Tvergaard, 2008, 2009; Dahl et al., 2012; Nielsen et al., 2012; Tvergaard, 2012, 2015a) involving the shear loading of elementary porous cells, where softening due to changes of the void shape and orientation was very apparent. It is found that with a simple, heuristic modelling of the phenomenon of mesoscopic strain localization, the model is indeed able to reproduce the results of these numerical experiments, in contrast to Gurson's model disregarding void shape effects

Inverse skull conductivity estimation problems from EEG data

International audienceA fundamental problem in theoretical neurosciences is the inverse problem of source localization, which aims at locating the sources of the electric activity of the functioning human brain using measurements usually acquired by non-invasive imaging techniques, such as the electroencephalography (EEG). EEG measures the effect of the electric activity of active brain regions through values of the electric potential furnished by a set of electrodes placed at the surface of the scalp and serves for clinical (location of epilepsy foci) and functional brain investigation. The inverse source localization problem in EEG is influenced by the electric conductivities of the several head tissues and mostly by the conductivity of the skull. The human skull isa bony tissue consisting of compact and spongy bone compartments, whose shape and size vary over the age and the individual’s anatomy making difficult to accurately model the skull conductivity

Spoken communicative intents among 3- to 4.5-year-old french-speaking children : procedure and data from the early longitudinal languageand neglect study

Purpose: This study aimed to: 1- provide speech-language pathologists and researchers with a play-based procedure to measure the expression of communicative intents by children aged 3 to 4.5 years, and 2- present indicators of these children’s capacity to produce these intents in this context. Method: A TRIAGE-inspired method allowed an advisory group of 16 speech-language pathologists to select and agree on definitions of intents to include in this procedure, among a set of 13 pre-selected intents based on the scientific literature. A longitudinal design including four measuring times was used to verify the production of these intents by 99 French speaking children (46 boys; Mage = 36;09 months) at 36, 42, 48, and 54 months using the Neighbourhood Game, a previously developed elicitation procedure of communicative intents conducted within the context of symbolic play. For each measurement time, the average percentage of children who had produced each intent at least three times was calculated with a 95% confidence interval. Non-parametric ANOVA for longitudinal data were carried out to verify progression with age. Results: A finalised list of eight communicative intents was selected along with their definition and a standardized script to elicit them during symbolic play. The production frequency of most intents showed significant progression between the first and the fourth measurement time. Arguing is the only intent which is still not produced by more than 90% of children at the age of 54 months. Conclusions: This study led to the development of an assessment procedure which presents ecological validity and elicits the expression of eight communicative intents among 3- to 4.5-year-olds. This procedure can support the work of speech-language pathologists and researchers

Spoken communicative intents among 3- to 4.5-year-old french-speaking children : procedure and data from the early longitudinal language and neglect study

Purpose: This study aimed to (a) provide speech-language pathologists and researchers with a play-based procedure to measure the expression of spoken communicative intents by children aged 3 to 4.5 years and (b) present indicators of these children’s capacity to produce these intents in this context. Method: A method inspired by TRIAGE (Technique de Recherche d’Informations par Animation d’un Group d’Experts) allowed an advisory group of 16 speechlanguage pathologists to select and agree on definitions of intents to include in this procedure, among a set of 13 preselected intents based on the scientific literature. A longitudinal design including four measuring times was used to verify the production of these intents by 99 French-speaking children (46 boys; Mage = 36.09 months) at 36, 42, 48, and 54 months using the Neighborhood Game, a previously developed elicitation procedure of communicative intents conducted within the context of symbolic play. For each measurement time, the average percentage of children who had produced each intent at least 3 times was calculated with a 95% confidence interval. Nonparametric analysis of variance for longitudinal data was carried out to verify progression with age. Results: A finalized list of eight communicative intents was selected along with their definition and a standardized script to elicit them during symbolic play. The production frequency of most intents showed significant progression between the first and the fourth measurement time. Arguing is the only intent that is still not produced by more than 90% of children at the age of 54 months. Conclusions: This study led to the development of an assessment procedure, which presents ecological validity and elicits the expression of eight communicative intents among 3- to 4.5-year-olds. This procedure can support the work of speech-language pathologists and researchers. The accompanying indicators of children’s capacity to produce these intents at a given age in this kind of context are a notable addition to the knowledge on typical language development

Morphosyntactic development and severe parental neglect in 4-year-old French-speaking children : ELLAN Study

Language is the most frequently compromised area of development in English-speaking neglected children, particularly the morphosyntactic component of language. This is very worrisome given its central role in academic success and social participation. No previous study has examined the morphosyntactic skills of French-speaking neglected children, despite the morphological richness of French. This study aimed to fill this gap. Forty-four neglected (mean age ¼ 48.32 months, SD ¼ 0.45) and 92 non-neglected (mean age ¼ 48.07 months, SD ¼ 0.24) French-speaking children participated. Measures of morphosyntactic skills were derived from a sample of spontaneous language collected during standardized semistructured play and analyzed using Systematic Analysis of Language Transcripts software (2012) . Four morphosyntactic indicators were compared using analyses of variance and Kolmogorov–Smirnov tests: the mean length of utterances (MLU), verbal inflections, word-level errors, and omission errors. The results indicate that 25.6% of the neglected children presented clinically significant morphosyntactic difficulties, as evidenced by a significantly shorter MLU (M ¼ 5.60, SD ¼ 1.13; M ¼ 6.90, SD ¼ 1.30), fewer verbal inflections, and more frequent word omission errors compared to their non-neglected peers. The results confirm that French-speaking neglected children present many morphosyntactic difficulties. This study argues for sustained speech–language services for these children

Vers une transition forestière en Thaïlande? : analyse causale de l’avancée des forêts à partir du cas de Phetchabun

Selon des thèses développées au cours des années 1990 et 2000, le développement économique constitue à la fois la source et la solution aux problèmes environnementaux. Au sujet des forêts, les transitions forestières (c’est-à-dire le passage de la déforestation à la reforestation) documentées dans certains pays développés seraient causées par des dynamiques universelles intrinsèques au développement et à la modernisation des sociétés. Nos travaux ont porté sur l’application de cette vision optimiste et controversée à l’évolution des superficies forestières en Thaïlande. S’appuyant sur une recension de la littérature, sur des données secondaires ainsi que nos travaux de terrain dans la région de Phetchabun, la thèse offre les apports suivants. Elle démontre que contrairement à l’idée répandue en Thaïlande, le ralentissement de la déforestation a été suivi par une expansion forestière substantielle entre environ 1995 et 2005. Ce regain forestier est lié à la disparition presque complète de l’expansion agricole, à l’établissement de plantations sylvicoles et, surtout, à l’abandon de terres agricoles. Cet abandon agricole découle d’abord et avant tout de la faible et incertaine rentabilité de l’agriculture dans certaines zones non irriguées. Ce phénomène s’explique, entre autres, par la dégradation des sols et par l’incapacité des agriculteurs à contrer l’impact des transformations économiques internes et externes à la Thaïlande. L’accroissement de la pression de conservation n’a pu contribuer à l’expansion forestière que dans certains contextes (projets de reforestation majeurs appuyés par l’armée, communautés divisées, terres déjà abandonnées). Sans en être une cause directe, l’intensification agricole et la croissance des secteurs non agricoles ont rendu moins pénibles la confiscation et l’abandon des terres et ont permis que de tels phénomènes surviennent sans entraîner d’importants troubles sociaux. Dans un contexte d’accroissement des prix agricoles, notamment celui du caoutchouc naturel, une partie du regain forestier aurait été perdu depuis 2005 en raison d’une ré-expansion des surfaces agricoles. Cela illustre le caractère non permanent de la transition forestière et la faiblesse des mesures de conservation lorsque les perspectives de profit sont grandes. La thèse montre que, pour être robuste, une théorie de la transition forestière doit être contingente et reconnaître que les variables macro-sociales fréquemment invoquées pour expliquer les transitions forestières (ex. : démocratisation, intensification agricole, croissance économique) peuvent aussi leur nuire. Une telle théorie doit également prendre en compte des éléments d’explication non strictement économiques et souvent négligés (menaces à la sécurité nationale, épuisement des terres perçues comme arables et libres, degré d’attachement aux terres et capacité d’adaptation et résilience des systèmes agricoles). Finalement, les écrits sur la transition forestière doivent reconnaître qu’elle a généralement impliqué des impacts sociaux et même environnementaux négatifs. Une lecture de la transition forestière plus nuancée et moins marquée par l’obsession de la seule reforestation est seule garante d’une saine gestion de l’environnement en respect avec les droits humains, la justice sociale et le développement durable.Recent popular ideas and theories portray economic development as both a cause and a solution to environmental degradation. Concerning forest cover, many authors view forest transitions (the passage from deforestation to reforestation) as resulting from near-universal causal dynamics linked to economic development. The thesis evaluates the validity of these controversial ideas and their relevance to the Thai case. Based on an analysis of secondary literature and official data as well as extensive fieldwork in Phetchabun region, the thesis makes the following points. Contrary to the dominant view, forest cover did expand significantly between ~1995 and 2005. Forest regrowth is linked to the near-interruption of agricultural expansion, the establishment of forest plantations, and, most importantly, agricultural abandonment. The latter derives first and foremost from the declining and currently uncertain profitability of agriculture in non-irrigated zones. These agricultural problems are linked to declining soil fertility and the incapacity of some farmers to counter the impact of rapid economic changes occurring within and outside Thailand. Conservation efforts contributed to forest expansion only in some contexts (ex.: military-backed projects, divided communities, land already abandoned). Agricultural intensification and the growth of non-agricultural sectors made land confiscation and agricultural abandonment less distressing and allowed these land transformations to occur without leading to major social troubles. Since 2005, part of the forest regrowth has been lost to the rubber boom. This illustrates both the potentially non-permanent nature of the forest transition and the limited power of forest conservation in the face of major politico-economic interests. A robust forest transition theory must be contextually-bounded and recognize that forest transitions can be encouraged, blocked or countered by the same frequently invoked macro-social variables: economic growth, agricultural intensification, and democratisation. It must also take into account neglected causal factors, such as geopolitical threats, the resilience of agrarian systems, the perception of land scarcity and the degree of attachment to the land and an agrarian life. Typically, social distress, violence and, in some cases, negative environmental impacts have accompanied forest transitions. Human rights, social justice and sustainable development principles require that a more nuanced view of forest transitions be adopted

Source localization using rational approximation on plane sections

N° RR-7704 http://hal.inria.fr/inria-00613644International audienceIn functional neuroimaging, a crucial problem is to localize active sources within the brain non-invasively, from knowledge of electromagnetic measurements outside the head. Identification of point sources from boundary measurements is an ill-posed inverse problem. In the case of electroencephalography (EEG), measurements are only available at electrode positions, the number of sources is not known in advance and the medium within the head is inhomogeneous. This paper presents a new method for EEG source localization, based on rational approximation techniques in the complex plane. The method is used in the context of a nested sphere head model, in combination with a cortical mapping procedure. Results on simulated data prove the applicability of the method in the context of realistic measurement configurations